One type of electronic equipment is, for example, a temperature controller where the temperature of an item, serving as the object of the temperature control, is controlled by turning ON or OFF the power source of a heater used for heating the object of the temperature control. The heating is performed in relation to a predetermined control temperature set for the object of the temperature control.
Such a temperature controller is configured using a plurality of electronic components installed and used in a control panel or the like on the side of an external device. The temperature controller accommodates a control board configuring a control unit for controlling the external device, a terminal to be electrically connected to the external device, and the like in an electronic equipment casing. Among temperature controllers, a known type is one provided with a display portion configured to dispose an LCD indicator unit on the front portion side of an electronic equipment casing so as to display a heating target temperature and a current temperature of a heat plate or the like in the indicator (refer to Patent Document 1 to Patent Document 3).
A temperature controller type widely used is one in which an LCD indicator unit is adopted as the display portion for a downsizing of the entire structure of the temperature controller and improvement of the display function. Such an LCD indicator unit is required to have an LCD indicator disposed in a front surface portion of the electronic equipment casing for displaying the target temperature and the current temperature, and have backlight means for radiating a back surface of the LCD indicator with backlight. Due to this, the temperature controller provided with the display portion is configured to accommodate such a LED display unit and the backlight means in the electronic equipment casing.
A backlight module such as described in Patent Document 4, for example, could be used as the backlight means for radiating the back surface of the LCD indicator. However, such a backlight module requires an electric connection, such as made by thermo-compression and soldering of a flexible substrate, a mount pin, and the like for providing an electric interface, and an increase in assembling man-hour and a rise in the cost of parts are unavoidable.
Thus, this type of conventional temperature controller provided with the display portion has for example a structure shown in FIG. 1. That is, in FIG. 1, in a temperature controller 1 serving as the electronic equipment, a display region portion 6a is exposed as a display portion of an LCD indicator 6 for displaying a set temperature value and the like and operation buttons 3 for operating a control unit and the like are disposed in a front surface portion of the electronic equipment casing 2. The control unit described later and the like are accommodated in the electronic equipment casing 2.
As shown in FIG. 7, this type of conventional temperature controller 1 has the electronic equipment casing 2 formed of a front case 2a and a rear case 2b. In a front surface portion of the front case 2a, a display window 2a-1 formed of an opened window, a closed window closing the opened window with transparent resin, and the like is provided, and a display window cover 4 formed into a frame shape or having a display window portion made of transparent resin is attached. A support frame body 2a-2 is formed so as to extend on the rear portion side of the front case 2a. In the support frame body 2a-2 are a display sheet 5 having a center portion formed as an opened window, a closed window closing the opened window with transparent resin, and the like, the LCD indicator 6 having the display region portion 6a on a front surface, a diffusion sheet 7, a reflective plate 8, and an LCD indicator control substrate 9 in which LEDs 9a serving as backlight sources for the LCD indicator 6 and a control circuit for performing LCD drive control, temperature adjustment control, and the like are mounted, and are successively fitted and disposed side by side from the back surface side of the front surface portion of the front case 2a to the rear side. The LCD indicator 6 and the LCD indicator control substrate 9 provide the electric interface via a pair of upper and lower rubber connectors 11 disposed in the front case 2a. An LCD indicator unit 10 is configured by the LCD indicator 6, the diffusion sheet 7, the reflective plate 8, and the LCD indicator control substrate 9 having the LEDs 9a, and possibly including the rubber connectors 11 and the display sheet 5.
Further, the rear case 2b has a box shape in which a front surface portion and a rear surface portion are opened. A terminal base 12 to be electrically connected to an external device is installed in a rear opening in a protruding manner, and a control unit substrate group 13 for controlling the external device via the terminal base 12 is accommodated inside. In the rear case 2b, the LCD indicator unit 10 is accommodated and installed so as to provide an electric interface with the control unit substrate group 13.
The temperature controller 1 configured in such a way is installed in a control panel or the like installed in a factory or the like. By operating the operation buttons 3 provided in the front surface portion of the front case 2a, the set temperature is digitally displayed in a set temperature display portion 6a-1 in the display region portion 6a of the LCD indicator 6 (refer to FIG. 1). At the same time, a current temperature indicating a heating state of an item serving as an object of temperature control in the external device, such as a heater operated based on such a set temperature, is digitally displayed in a current temperature display portion 6a-2 in the display region portion 6a. 
Digital display of the set temperature display portion 6a-1 and the current temperature display portion 6a-2 in the display region portion 6a is performed by control of the LCD indicator control substrate 9 disposed on the rear portion side of the LCD indicator 6, with the LCD indicator control substrate 9 similarly configuring the LCD indicator unit 10, or the like. That is, in the LCD indicator unit 10, an operation signal of the operation buttons 3 is firstly received by the LCD indicator control substrate 9. The set temperature is digitally expressed by the LCD indicator 6, and displayed characters of the set temperature display portion 6a-1 in the display region portion 6a are transparently displayed by illumination of the LEDs 9a, so that the set temperature is digitally displayed. Similarly, in a case where the current temperature signal indicating the heating state of the item in the external device is received by the LCD indicator control substrate 9 via the control unit substrate group 13, the current temperature is digitally expressed by the LCD indicator 6, and the displayed characters are similarly transparently displayed by the illumination of the LEDs 9a in the current temperature display portion 6a-2 of the display region portion 6a, so that the current temperature is digitally displayed.
In such a way, in order to make the LCD indicator 6 clearly display the set temperature and the current temperature in the display region portion 6a, the temperature controller 1 is required to include backlight means for illuminating a rear surface of the LCD indicator 6. Therefore, the LEDs 9a are mounted on the LCD indicator control substrate 9 so as to face a digital display portion of the display region portion 6a in the LCD indicator 6. A light beam of the LEDs 9a applied by lighting of the LEDs 9a is diffused by the diffusion sheet 7 so as to spread over the entire display region portion 6a, while preventing diffusion to an exterior of the display region portion 6a by the reflective plate 8. The LCD indicator 6 displays the generated digital display in the display region portion 6a, so that a user can visually recognize it.